Objective: To carry out the in vitro protein synthesis in cell-free extracts programmed by Rous sarcoma virion RNA or messenger RNA (mRNA) from uninfected cells. Approach: Cell-free extracts have been prepared from wheat germ. Rous sarcoma virus RNA or mRNA from uninfected or transformed chick embryo fibroblasts will be translated into polypeptides. The polypeptide products of synthesis will be analyzed by immunoprecipitation with antibodies against disrupted virions and by two-dimension peptide fingerprinting. Since virion RNA probably is a polycistronic message it should program the synthesis of all the polypeptides encoded by the Rous sarcoma virus genome. Therefore a search for non-virion proteins will be carried out.